Shield Guardian

+6: The guardian is able to pass a DC 20 Strength check without taking damage (i.e. fire from a burning timber, or bludgeoning from catching a stone)
+15: Spell Storing: The construct may cause an ally to charge him with a spell, costing their reaction. He is then allowed to cast that spell once.
+20: Spell Tuned: The construct does the same as above, but with no cost of reaction or spell slot from the original castor.